1. Field of the Invention
This invention relates to a continuous torque transmission having a torque converter and providing torque during shifting of gears.
One of the best known means to solve this problem of continuous torque transmission during shifting is that of the automatic transmission. From the economic viewpoint this solution has the drawback of requiring putting well lapped means in place and, for the user, the drawbacks of weight and efficiency.
Another torque transmission device has been developed which relates to the use of a converter ahead of the manual transmission. This is well known and, in particular, makes it possible to assure the phases of starting and reclutching during shifting in a perfect way, which is not the case with a single dry friction clutch, all the more so since the use in parallel of a clutch locking the converter makes it possible not to lose efficiency.
This system thus realized still has a drawback: the interruption of the torque (engine or brake) transmitted to the wheels during shifting. This is reflected by a loss of efficiency and mobility in the general case and is a hinderance to automation of shifting. Actually, in this latter case, since the automatic device cannot take all factors of the environment into account, no matter how sophisticated the automatic device may be, there will always be cases where shifting be ill-timed for the driver. This interruption in torque transmission can even present a danger. To illustrate this point, the case can be considered of a vehicle passing on an incline and where the automatic device shifts to a higher gear. The interruption of torque during the necessary fraction of a second handicaps the vehicle and makes the maneuver dangerous. In this case, only palliatives such as locking of the shifting can be used.